Finding values in a matrix with logical operation

1 次查看（过去 30 天）
MiauMiau
MiauMiau 2013-1-9
Hi
I know how to show for a Matrix A the values in the first column which fullfill a certain condition. Say:
A =
8 1 6
3 5 7
4 9 2
Then I could use for displaying all the values bigger then 3 in the first column the following line:
A(A(:,1) > 3)
But what line do I use, if I want to display the values in the second column which are bigger than say "3"?
Thanks
  1 个评论
Matt J
Matt J 2013-1-9
编辑：Matt J 2013-1-9
Then I could use for displaying all the values bigger then 3 in the first column the following line: A(A(:,1) > 3)
While this would work in the case of the first column, it is cleaner to specify the column number explicitly not just in the indexing expression, but also in the look-up expression
A(A(:,1) > 3, 1 )
It's also easier to see how to generalize it to other columns, as Jan has showed you.

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Jan
Jan 2013-1-9
编辑：Jan 2013-1-9
A strange question. What about replacing the column index 1 by 2?
A(A(:, 2) > 3, 2)
Explicitly:
v = A(:, 2);
v(v > 3)
  1 个评论
MiauMiau
MiauMiau 2013-1-9
sorry for the strange question. I was not aware that it is possible to use booleans in that way, since A(:,2) > 3 in our case returns a boolean 3,1-Matrix, whereas the index for the column is just the 1,1 matrix "2". That's not so obvious to come up with for a beginner.

请先登录，再进行评论。

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Creating and Concatenating Matrices 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by